The conventional weather forecast process is typically organized along a forecast assembly line that is termed “human-in-the-loop” (HITL) or Meteorologist in the loop (MITL). The process begins with the rapid and near real-time collection and organization of a single numerical or statistical weather prediction model (NWP or Model Output Statistics—MOS) or, more commonly, a plurality of NWP's and MOS's (loosely called Statistical Weather Prediction or SWP since they represent some ensemble or composite or smart assemblage of real-time prediction of the weather for the same time and space). These forecasts are provided for a set of parameters in two or three spatial dimensions (for example temperature, chance of precipitation, winds, and humidity) usually at regularly spaced points within some domain or over the entire earth (a so-called gridded forecast), at some time step or interval (the forecast time step or temporal resolution), and for some period into the future (the weather forecast duration or valid time). The most recent or contemporaneous collection of these objective gridded digital forecasts is called “guidance” since it represents the starting point or “first-guess” for the HITL forecaster.
Using computer visualization and graphical editing tools, the HITL forecaster reviews, edits, applies quality-controls, and adds human meteorological expertise (value-add) to this grid (or cube or N-dimensional collection) of weather forecast elements. The editing of the perishable forecast data is performed as quickly as possible, but there is often a great deal of activity in this editing window or time interval with multiple forecasters, working on many weather variables, over large domains, and even in different physical forecast offices or locations. Sometimes, the HITL forecaster will choose to withhold new guidance as an input to their editing system; instead, they will keep the modified “going” digital forecast since this will reduce rework and might speed the movement along the HITL assembly line. Since weather elements are continuous in space and time (for example, the predicted temperature 12 hours in the future)—the HITL process will generally hold the guidance or initial forecast until all review and changes are made by the forecast staff. Finally, the edited forecasts are released or pushed to downstream systems or users. Here, the digital forecasts can be translated and post-processed into the familiar weather content we see today on TV, web sites, digital devices, and other content platforms.
In the current HITL paradigm, there are interrelated factors that conspire to weather forecast skill, i.e., they reduce the expected skill of the man-machine forecast. For example, due to continuity, forecast edits cannot be made piecemeal. The entirety of the guidance is withheld from the downstream processing and publishing until the review and editing task is complete. If the area of responsibility of a forecast is large and the spatial and temporal resolution is fine-scale, the time taken to review and edit many weather elements at many time steps can be long; perhaps 2-3 hours in total elapsed time.
The granularity of NWP and SWP forecasts (guidance) is rapidly increasing over time. There are global models or simulations with spatial resolution on the order of 10 km (about 10 million gridpoints on the earth's surface), and there are regional models with resolution on the order of 1 km (this would be about 10 million gridpoints in the Conterminous United States or CONUS). Temporal resolution is typically 1 to 3 hours for these same models, and the models can run as much as 384 hours into the future (16 days). Most importantly, the models are run multiple times per day. Global models are now typically running 4× daily and regional models (on the scale of CONUS) may run hourly. This rapidly flowing output represents huge amounts of data for both machine and forecaster to digest.
In the HITL process, the forecaster must corral at least a portion of this voluminous forecast guidance into a holding pen. Once there, the guidance is cleaned and edited to a point where it is acceptable for downstream consumption. While the HITL process takes place, more guidance is arriving upstream, and simultaneously, the downstream forecasts are aging. The technological and scientific boon of higher resolution and more varied NWP and SWP—and more frequent NWP and SWP—creates a critical dilemma for the HITL forecaster and forecast process, and one that will exacerbate with time as guidance becomes more voluminous in time and space and variety.